diff --git a/apps/web/src/widgets/map3d/Map3D.tsx b/apps/web/src/widgets/map3d/Map3D.tsx
index d3da34b..13ca7ae 100644
--- a/apps/web/src/widgets/map3d/Map3D.tsx
+++ b/apps/web/src/widgets/map3d/Map3D.tsx
@@ -997,14 +997,20 @@ function injectOceanBathymetryLayers(style: StyleSpecification, maptilerKey: str
   } as unknown as LayerSpecification;
 
   // Insert before the first symbol layer (keep labels on top), otherwise append.
-  const rawLayers = Array.isArray(style.layers) ? style.layers : [];
-  const layers = rawLayers.filter((layer): layer is LayerSpecification => {
-    if (!layer || typeof layer !== "object") return false;
-    return typeof (layer as { id?: unknown }).id === "string";
-  });
-  const symbolIndex = layers.findIndex((l) => l.type === "symbol");
+  const layers = Array.isArray(style.layers) ? (style.layers as unknown as LayerSpecification[]) : [];
+  if (!Array.isArray(style.layers)) {
+    style.layers = layers as unknown as StyleSpecification["layers"];
+  }
+
+  const symbolIndex = layers.findIndex((l) => (l as { type?: unknown } | null)?.type === "symbol");
   const insertAt = symbolIndex >= 0 ? symbolIndex : layers.length;
 
+  const existingIds = new Set<string>();
+  for (const layer of layers) {
+    const id = getLayerId(layer);
+    if (id) existingIds.add(id);
+  }
+
   const toInsert = [
     bathyFill,
     bathyBandBorders,
@@ -1013,12 +1019,44 @@ function injectOceanBathymetryLayers(style: StyleSpecification, maptilerKey: str
     bathyLinesMajor,
     bathyLabels,
     landformLabels,
-  ].filter(
-    (l) => !layers.some((x) => x.id === l.id),
-  );
+  ].filter((l) => !existingIds.has(l.id));
   if (toInsert.length > 0) layers.splice(insertAt, 0, ...toInsert);
 }
 
+type BathyZoomRange = {
+  id: string;
+  mercator: [number, number];
+  globe: [number, number];
+};
+
+const BATHY_ZOOM_RANGES: BathyZoomRange[] = [
+  { id: "bathymetry-fill", mercator: [6, 12], globe: [8, 12] },
+  { id: "bathymetry-borders", mercator: [6, 14], globe: [8, 14] },
+  { id: "bathymetry-borders-major", mercator: [4, 14], globe: [8, 14] },
+];
+
+function applyBathymetryZoomProfile(map: maplibregl.Map, baseMap: BaseMapId, projection: MapProjectionId) {
+  if (!map || !map.isStyleLoaded()) return;
+  if (baseMap !== "enhanced") return;
+  const isGlobe = projection === "globe";
+
+  for (const range of BATHY_ZOOM_RANGES) {
+    if (!map.getLayer(range.id)) continue;
+    const [minzoom, maxzoom] = isGlobe ? range.globe : range.mercator;
+    try {
+      // Safety: ensure heavy layers aren't stuck hidden from a previous session.
+      map.setLayoutProperty(range.id, "visibility", "visible");
+    } catch {
+      // ignore
+    }
+    try {
+      map.setLayerZoomRange(range.id, minzoom, maxzoom);
+    } catch {
+      // ignore
+    }
+  }
+}
+
 async function resolveInitialMapStyle(signal: AbortSignal): Promise<string | StyleSpecification> {
   const key = getMapTilerKey();
   if (!key) return "/map/styles/osm-seamark.json";
@@ -1223,6 +1261,7 @@ export function Map3D({
   const projectionBusyTokenRef = useRef(0);
   const projectionBusyTimerRef = useRef<ReturnType<typeof window.setTimeout> | null>(null);
   const projectionPrevRef = useRef<MapProjectionId>(projection);
+  const bathyZoomProfileKeyRef = useRef<string>("");
   const mapTooltipRef = useRef<maplibregl.Popup | null>(null);
   const deckHoverRafRef = useRef<number | null>(null);
   const deckHoverHasHitRef = useRef(false);
@@ -2081,33 +2120,25 @@ export function Map3D({
   }, [baseMap]);
 
   // Globe rendering + bathymetry tuning.
-  // Some terrain/hillshade/extrusion effects look unstable under globe and can occlude Deck overlays.
+  // Under globe projection, low-zoom bathymetry polygons can exceed MapLibre's per-segment 16-bit vertex
+  // limit (65535) due to projection subdivision. Keep globe stable by gating heavy bathymetry fills/borders
+  // to higher zoom levels rather than toggling them on every frame.
   useEffect(() => {
     const map = mapRef.current;
     if (!map) return;
 
     const apply = () => {
       if (!map.isStyleLoaded()) return;
-      const disableBathyHeavy = projection === "globe" && baseMap === "enhanced";
-      const visHeavy = disableBathyHeavy ? "none" : "visible";
       const seaVisibility = "visible" as const;
       const seaRegex = /(water|sea|ocean|river|lake|coast|bay)/i;
 
-      // Globe + our injected bathymetry fill polygons can exceed MapLibre's per-segment vertex limit
-      // (65535), causing broken ocean rendering. Keep globe mode stable by disabling the heavy fill.
-      const heavyIds = [
-        "bathymetry-fill",
-        "bathymetry-borders",
-        "bathymetry-borders-major",
-        "bathymetry-extrusion",
-        "bathymetry-hillshade",
-      ];
-      for (const id of heavyIds) {
-        try {
-          if (map.getLayer(id)) map.setLayoutProperty(id, "visibility", visHeavy);
-        } catch {
-          // ignore
-        }
+      // Apply zoom gating for heavy bathymetry layers once per (baseMap, projection) combination.
+      // This avoids repeatedly mutating layer zoom ranges on hover/mapSyncEpoch pulses.
+      const nextProfileKey = `bathyZoomV1|${baseMap}|${projection}`;
+      if (bathyZoomProfileKeyRef.current !== nextProfileKey) {
+        applyBathymetryZoomProfile(map, baseMap, projection);
+        bathyZoomProfileKeyRef.current = nextProfileKey;
+        kickRepaint(map);
       }
 
       // Vector basemap water layers can be tuned per-style. Keep visible by default,